Tilt rotor aircraft with fixed engine arrangement

ABSTRACT

The system of the present application includes an engine and pylon arrangement for a tilt rotor aircraft in which the engine is fixed in relation to a wing portion of the aircraft, while the pylon is rotatable. The pylon supports a rotor hub having a plurality of rotor blades. Rotation of the pylon allows the aircraft to selectively fly in a helicopter mode and an airplane mode, as well as any combination thereof.

This application claims the benefit of U.S. Provisional PatentApplication No. 61/439,547 filed 4 Feb. 2011, titled “TILT ROTORAIRCRAFT WITH FIXED ENGINE ARRANGEMENT;” and is a continuation of U.S.patent application Ser. No. 13/357,981 filed 25 Jan. 2012, titled “TILTROTOR AIRCRAFT WITH FIXED ENGINE ARRANGEMENT,” all of which are herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Technical Field

The present application relates to an engine and pylon configuration fora tilt rotor aircraft.

2. Description of Related Art

A typical tilt rotor aircraft has wing mounted rotatable nacelles, eachnacelle having an engine and rotor hub. The nacelles are selectivelyrotated between a helicopter mode and an airplane mode. During thehelicopter mode, the nacelles are rotated to an approximate verticalposition so that the tilt rotor aircraft can hover similar to aconventional helicopter. During the airplane mode, the nacelles arerotated to an approximate horizontal position so that the tilt rotoraircraft can fly similar to a fixed wing aircraft. Because the engine islocated in the nacelle, the engine must be configured and certified tooperate not only in a horizontal orientation, but also a verticalorientation, thus limiting engine choices. Further, a rotating enginetypically requires more maintenance than a fixed engine. Even further, arotating engine typically requires complex engine mounting structure,thus limiting maintenance/inspection access around the engine.

Hence there is a need for an improved engine and pylon configuration fora tilt rotor aircraft.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the system of the presentapplication are set forth in the appended claims. However, the systemitself, as well as a preferred mode of use, and further objectives andadvantages thereof, will best be understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a tilt rotor aircraft, according to thepreferred embodiment of the present application;

FIG. 2 is a perspective view of the rotor system, according to thepreferred embodiment of the present application;

FIG. 3 is a perspective view of the rotor system, according to thepreferred embodiment of the present application;

FIG. 4 is a perspective view of the rotor system, according to thepreferred embodiment of the present application;

FIG. 5 is a partial perspective view of the rotor system, according tothe preferred embodiment of the present application;

FIG. 6 is a partial perspective view of the rotor system, according tothe preferred embodiment of the present application;

FIG. 7 is a partial perspective view of the rotor system, according tothe preferred embodiment of the present application;

FIG. 8 is a perspective view of a tilt rotor aircraft, according to analternative embodiment of the present application;

FIG. 9 is a perspective view of the rotor system, according to analternative embodiment of the present application; and

FIG. 10 is a partial perspective view of the rotor system, according toan alternative embodiment of the present application.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the system of the present application aredescribed below. In the interest of clarity, not all features of anactual implementation are described in this specification. It will ofcourse be appreciated that in the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the device described herein may beoriented in any desired direction.

The system of the present application includes an engine and pylonarrangement for a tilt rotor aircraft in which the engine is fixed inrelation to a wing portion of the aircraft, while the pylon isrotatable. The pylon supports a rotor hub having a plurality of rotorblades. Rotation of the pylon allows the aircraft to selectively fly ina helicopter mode and an airplane mode, as well as any combinationthereof.

Referring to FIG. 1, a tilt rotor aircraft 101 is illustrated. In theillustrated embodiment, tilt rotor aircraft 101 includes a fuselage 103,a wing member 105, and a tail member 107. Aircraft 101 further includesa first rotor system 109 a and a second rotor system 109 b. First rotorsystem 109 a is located on a left end portion of wing member 105, whilesecond rotor system 109 b is located on a right end portion of wingmember 105. First rotor system 109 a and second rotor system 109 b aresubstantially symmetric of each other. In the interest of clarity, onlyfirst rotor system 109 a will be discussed in detail. However, one ofordinary skill in the art will understand that the form and function ofsecond rotor system 109 b will be fully known from the benefit of thedisclosure herein related to first rotor system 109 a. Furthermore,first rotor system 109 a and second rotor system 109 b each includerotor blades 111 a and 111 b, respectively. However, in the interest ofclarity, rotor blades 111 a and 111 b are omitted from some drawingviews.

It should be appreciated that even though first rotor system 109 a andsecond rotor system 109 b are illustrated on tilt rotor aircraft 101,first rotor system 109 a and second rotor system 109 b can beimplemented on other tilt rotor aircraft. For example, an alternativeembodiment can include a quad tilt rotor aircraft that has an additionalwing member located aft of wing member 105, the additional wing membercan have additional rotor systems similar to first rotor system 109 aand second rotor system 109 b. Another alternative embodiment caninclude an unmanned version of tilt rotor aircraft 101. Further, firstrotor system 109 a and second rotor system 109 b can be integrated intoa variety of tilt rotor aircraft configurations.

Referring now to FIGS. 2 and 3, rotor system 109 a is illustrated in anairplane mode and a helicopter mode, respectively. Rotor system 109 aincludes an outboard fixed engine nacelle 113 and an inboard fixedengine nacelle 115. A prop-rotor pylon 119 includes a plurality of rotorblades 111 a (shown in FIG. 1) coupled to internal rotor structurelocated within an aerodynamic spinner fairing 121. Prop-rotor pylon 119includes a nacelle fairing 123 that is configured to rotate along withother rotatable pylon structure. Rotor system 109 a can include amoveable fairing panel 125 that can be actuated in the aft direction inorder to provide rotational clearance for nacelle fairing 123 whenprop-rotor pylon 119 is actuated into helicopter mode. Further, moveablefairing panel 125 is actuated forward when prop-rotor pylon 119 isactuated into airplane mode so as to improve aerodynamic airflow aboutthe aft portion of prop-rotor pylon 119. Moveable fairing panel 125 canbe actuated with an independent actuator, or can be mechanically coupledto the actuator system used for actuating prop-rotor pylon 119 betweenairplane mode and helicopter mode.

Prop-rotor pylon 119 is rotatable between the airplane mode, in whichprop-rotor pylon 119 is positioned approximately horizontal (as shown inFIG. 2), and a helicopter mode (as shown in FIG. 3), in which prop-rotorpylon 119 is positioned approximately vertical. During the airplanemode, vertical lift is primarily supplied by the airfoil profile of wingmember 105, while rotor blades 111 a and 111 b in each prop-rotor pylon119 provide forward thrust. During the helicopter mode, vertical lift isprimarily supplied by the thrust of rotor blades 111 a and 111 b in eachprop-rotor pylon 119. It should be appreciated that tilt rotor aircraft101 may be operated such that prop-rotor pylons 119 are selectivelypositioned between airplane mode and helicopter mode, which can bereferred to as a conversion mode.

Rotor system 109 a can include a pylon downstop 127 for securingprop-rotor pylon 119 when prop-rotor pylon 119 is positioned in theairplane mode. Further, pylon downstop 127 can be beneficial forrelieving stresses on the actuator(s), such as a conversion actuator133, used for selectively rotating prop-rotor pylon 119 between airplanemode position and helicopter mode position.

Outboard fixed engine nacelle 113 includes an outboard engine air inlet114. Similarly, inboard fixed engine nacelle 115 includes an inboardengine air inlet 116. Air inlets 114 and 116 can be positioned aft of aleading edge portion 117 of wing member 105; however, an alternativeembodiment can include the positioning of air inlets 114 and 116 forwardof leading edge portion 117 of wing member 105. The exact position ofair inlets 114 and 116 is implementation specific and dependent in partupon the aerodynamic ram air effects that can be achieved throughselective placement.

It should be appreciated that the wing tip portion of wing member 105can be lengthened to customize an aspect ratio of wing member 105 inaccordance with implementation specific aerodynamic lift requirements.As such, it should be understood that even though outboard fixed enginenacelle 113 is illustrated approximately abutting the wing tip portionof wing member 105, an alternative embodiment may include the wing tipportion extending well beyond outboard fixed engine nacelle 113.

When rotor system 109 a is in helicopter mode, airflow downwash fromrotor blades 111 a and 111 b can flow, when uninhibited, along the uppersurface of wing member 105, thereby negatively affecting vertical liftperformance. Inboard fixed engine nacelle 115 is located in part to actas an air dam to thwart downwash airflow along the upper surface of wingmember 105, the downwash airflow being in the direction from the rootend to the tip end of wing member 105.

Referring now also to FIGS. 4-7, rotor system 109 a is illustrated infurther detail. A swashplate 129 is coupled rotor blades 111 a via aplurality of pitch links (not shown). Swashplate actuators 131 a-131 care configured to selectively actuate swashplate 129, therebyselectively changing the pitch of rotor blades 111 a so as to affectthrust, lift, and direction of aircraft 101 during operation. Forexample, swashplate 129 can be selectively tilted to effect cyclic pitchchange of rotor blades 111 a. Further, swashplate 129 can be actuated toeffect collective pitch change of rotor blades 111 a. A conversionactuator 133 is configured to selectively actuate prop-rotor pylon 119between a helicopter mode position and an airplane mode position, whilethe engines 145 and 147 remain fixed on wing member 105. It should beappreciated that conversion actuator 133 may be of a variety ofconfigurations. For example, conversion actuator 133 may be a linearactuator or a rotary actuator, the exact actuator type beingimplementation specific. A prop-rotor gearbox housing 143 of prop-rotorpylon 119 is pivotally mounted on an outboard rib bearing 139 within anoutboard rib 135, and an inboard rib bearing 141 within an inboard rib137.

An outboard engine 145 and an inboard engine 147 can be structurallymounted on an engine support beam 149 near a trailing edge portion ofwing member 105. Outboard engine 145 is mechanically coupled to anoutboard input gearbox 151, via an outboard input driveshaft 155, suchthat torque is transferred to outboard input gearbox 151 from outboardengine 145. Similarly, inboard engine 147 is mechanically coupled to aninboard input gearbox 153, via an inboard input driveshaft 157, suchthat torque is transferred to inboard input gearbox 153 from inboardengine 147. Torque is transferred to a main rotor mast 163 from outboardinput gearbox 155 and inboard input gearbox via an outboard gearboxdriveshaft 159 and an inboard gearbox driveshaft, respectively.

Inboard input gearbox 153 can optionally be coupled to an accessoryinput gearbox 165 and further an interconnect drive shaft 167.Interconnect drive shaft 167 can be used to drive an auxiliary gearboxlocated within fuselage 103. In an alternative embodiment, interconnectdrive shaft 167 can be sized to carry torque sufficient to drive rotorblades 111 b on rotor system 109 b, which can provide an additionalsafety factor in an engine failure situation.

The configuration of rotor system 109 a allows engines 145 and 147 toremain fixed on wing member 105, while only prop-rotor pylon 119 rotatesto allow aircraft 101 to fly both in a helicopter mode, an airplanemode, and conversion mode. Attempts have been made in prior tilt rotoraircraft configurations to locate fixed engines within a fuselage of theaircraft; however, such a configuration requires an interconnect drivesystem to carry full engine power out to the wing tip mounted rotor andprop-rotor drive gearboxes, which can degrade safety and reliability ofthe drive system. In contrast, rotor system 109 a is configured suchthat the engines 145 and 147 are located directed adjacent to prop-rotorpylon 119, so that only a short input shaft system is required to carryfull engine power. As such, the short input drive shaft system from eachengine to the proprotor pylon provides increased safety, reliability,and efficiency. In the illustrated embodiment, full engine power iscarried in input driveshafts 155 and 157, as well as gearbox driveshafts 159 and 161. Further, by having two engines 145 and 147, a factorof safety is realized, thus an interconnect drive shaft configured tocarry engine power between rotor systems 109 a and 109 b is notrequired. However, having an interconnect drive shaft configured tocarry engine power between rotor systems 109 a and 109 b is analternative configuration that may be desirable when a significant hedgeagainst multiple engine failure is desired. Furthermore, configuringrotor system 109 a with fixed engines, instead of engines that rotate,results in a significant reduction in engine certification costs,complexity, and expense. Furthermore, a rotor system 109 a with fixedengines, instead of engines that rotate, can provide a substantialincrease in engine options and availabilities, thus contributing toaircraft cost reduction.

Referring now to FIGS. 8-10, a tilt rotor aircraft 801 is illustrated asan alternative embodiment of tilt rotor aircraft 101. Tilt rotoraircraft 801 is substantially similar in form and function to tilt rotoraircraft 801, except as noted herein. For example, tilt rotor aircraft801 is different from tilt rotor aircraft 101 in that inboard fixedengine nacelle 115 is omitted in rotor systems 809 a and 809 b. As such,tilt rotor aircraft 801 has only a single fixed engine in each rotorsystem 809 a and 809 b. Further, an optional wing fence 803 can beutilized to act as an air dam to thwart downwash airflow along the uppersurface of wing member 105, the downwash airflow being in the directionfrom the root end to the tip end of wing member 105. While tilt rotoraircraft 801 has only a single engine 145 for powering prop-rotor pylon119, it can be especially desirable for interconnect drive shaft 167 tobe sized to carry torque sufficient to drive rotor blades 111 b on rotorsystem 809 b, which can provide an additional safety factor in an enginefailure situation. In the illustrated embodiment, inboard input gearbox153 mechanically transmits power from outboard engine 145 to accessoryinput gearbox 165 and further to interconnect drive shaft 167. It shouldbe understood that the exact configuration of the drive shafts andgearboxes is implementation specific.

It is apparent that a rotor system with significant advantages has beendescribed and illustrated. The tilt rotor fixed engine system providesfor a horizontal, permanent engine mounting which reduces certificationcosts, increases available engine choices, and reduces maintenance costsand scheduled maintenance times. The proximity of the fixed engines tothe rotating pylon also increases safety with regard to drive shaftfailures, bearing lives, and coupling needs. Although the system of thepresent application is shown in a limited number of forms, it is notlimited to just these forms, but is amenable to various changes andmodifications without departing from the spirit thereof.

The invention claimed is:
 1. A rotor system for a tilt rotor aircraft,the rotor system comprising: an outboard engine in a first fixedlocation on a wing member of the tilt rotor aircraft; a prop-rotor pylonin power communication with the outboard engine, the prop-rotor pylonbeing configured to selectively rotate between a vertical position and ahorizontal position, the prop-rotor pylon comprising a plurality ofrotor blades; an outboard input drive shaft coupled between the outboardengine and an outboard input gearbox; and an outboard gearbox driveshaft being perpendicular to the outboard input drive shaft and coupledto the outboard input drive shaft; wherein the prop-rotor pylonselectively rotates about the outboard gearbox drive shaft whenorienting between the vertical position and the horizontal position; andwherein the prop-rotor pylon rotates relative to the wing member.
 2. Therotor system according to claim 1, wherein the outboard engine islocated outboard of the prop-rotor pylon.
 3. The rotor system accordingto claim 1, the prop-rotor pylon further comprising: a swashplate; agearbox; and a nacelle fairing configured as an aerodynamic housing forthe swashplate and the gearbox.
 4. The rotor system according to claim1, wherein the outboard gearbox drive shaft traverses through aninterior of an outboard rib bearing, the outboard rib bearing providingrotational support for the prop-rotor pylon against a fixed outboard ribmember.
 5. The rotor system according to claim 1, the prop-rotor pylonfurther comprising: a nacelle fairing configured as an aerodynamichousing for internal components located therein; a fairing panel locatedaft of the nacelle fairing, the fairing panel being moveable between aclosed position and an open position, the closed position providingaerodynamic efficiency when the prop-rotor pylon is the horizontalposition, the open position providing clearance for the prop-rotor pylonto rotate into the vertical position.
 6. The rotor system according toclaim 1, further comprising: an inboard engine in a second fixedlocation on the wing member of the tilt rotor aircraft.
 7. The rotorsystem according to claim 6, further comprising: an inboard input driveshaft coupled between the inboard engine and an inboard input gearbox;and an inboard gearbox drive shaft coupled between the inboard inputgearbox and a gearbox located in the prop-rotor pylon.
 8. The rotorsystem according to claim 7, further comprising: an accessory driveshaft coupled between the inboard input gearbox and an accessory inputgearbox; an interconnect drive shaft coupled to the accessory inputgearbox.
 9. The rotor system according to claim 8, wherein theinterconnect drive shaft is coupled to an accessory gearbox located in afuselage portion of the aircraft.
 10. The rotor system according toclaim 8, wherein the interconnect drive shaft is coupled to a gearboxconfigured for driving a second prop-rotor pylon located on an oppositeportion of the wing member.
 11. A tilt rotor aircraft comprising: afuselage; a wing member; an outboard engine in a first fixed location onthe wing member of the tilt rotor aircraft; an inboard engine in asecond fixed location on the wing member of the tilt rotor aircraft; anda prop-rotor pylon powered by the outboard engine and the inboardengine, the prop-rotor pylon being configured to selectively rotatebetween a vertical position and a horizontal position, the prop-rotorpylon comprising a plurality of rotor blades; wherein the outboardengine is located outboard of the prop-rotor pylon; wherein the inboardengine is located inboard of the prop-rotor pylon; and wherein theprop-rotor pylon rotates relative to the winq member.
 12. The tilt rotoraircraft according to claim 11, wherein the outboard engine and theprop-rotor pylon being located on an outboard portion of the wingmember, the outboard portion being a selected distance from thefuselage.
 13. The tilt rotor aircraft according to claim 11, theprop-rotor pylon further comprising: a swashplate; a gearbox; and anacelle fairing configured as an aerodynamic housing for the swashplateand the gearbox.
 14. The tilt rotor aircraft according to claim 11,further comprising: an outboard input drive shaft coupled between theoutboard engine and an outboard input gearbox; and an outboard gearboxdrive shaft coupled between the outboard input gearbox and a gearboxlocated in the prop-rotor pylon.
 15. The tilt rotor aircraft accordingto claim 14, wherein the outboard gearbox drive shaft traverses throughan interior of an outboard rib bearing, the outboard rib bearingproviding rotational support for the prop-rotor pylon against a fixedoutboard rib member.
 16. The tilt rotor aircraft according to claim 11,the prop-rotor pylon further comprising: a nacelle fairing configured asan aerodynamic housing for internal components located therein; afairing panel located aft of the nacelle fairing, the fairing panelbeing moveable between a closed position and an open position, theclosed position providing aerodynamic efficiency when the prop-rotorpylon is the horizontal position, the open position providing clearancefor the prop-rotor pylon to rotate into the vertical position.
 17. Thetilt rotor aircraft according to claim 11, wherein the prop-rotor pylonis located between the outboard engine and the inboard engine.
 18. Thetilt rotor aircraft according to claim 11, further comprising: aninboard input drive shaft coupled between the inboard engine and aninboard input gearbox; and an inboard gearbox drive shaft coupledbetween the inboard input gearbox and a gearbox located in theprop-rotor pylon.
 19. The tilt rotor aircraft according to claim 11,further comprising: a conversion actuator configured to selectivelyrotate the prop-rotor pylon.
 20. The tilt rotor aircraft according toclaim 11, wherein the outboard engine and the inboard engine aredirectly adjacent the prop-rotor pylon.